In gas turbine engines, such as disclosed in PCT International Publication WO No. 82/01033 by Karstensen published on Apr. 1, 1982 and also U.S. Pat. No. 4,030,288 issued to Davis et al on June 21, 1977, it has been conventional to provide one or more radially-resilient seals between a stator nozzle assembly and a surrounding housing which are telescopically assembled together. Such seals serve to seal an auxiliary cooling air stream, used to internally cool the stator nozzle vanes and perhaps other various high temperature portions of the gas turbine engine, from a much hotter main combustion gas stream used to propel the blades of a rotatable turbine rotor assembly.
Such seals must be radially resilient to accommodate differential thermal growth, as well as dimensional tolerances, between the overlapping housing and the relatively hotter stator nozzle assembly. For example, as shown in U.S. Pat. No. 4,268,046 issued to Nisper on May 19, 1981, each seal may comprise a plurality of axially stacked split-ring segments and a resilient annular expander. The expander is disposed radially inside all the split-ring segments in order to resiliently expand them radially outwardly against the housing.
One problem with the above arrangements is that the radially expandable seal frequently tends to completely spring out of its annular groove before or during telescopic assembly of the stator nozzle assembly and the overlapping housing. Furthermore, such telescopic assembly is a blind one in the sense that the seal becomes hidden from the assembler's view once the housing and the stator nozzle assembly are overlapped. Consequently, the assembler cannot see whether or not the seal has remained in its annular groove and is properly seated against the overlapping housing.
Improper installation of the seal can lead to a number of problems during gas turbine engine operation. First, the pressurized cooling air stream will leak past the unseated seal and will flow directly into the hot combustion gas stream at some angle that would cause undesirable turbulence and disruption of the relatively smooth flow lines of the hot combustion gas stream. Such disruption decreases the momentum of the hot combustion gas stream and consequently lowers the power output of the turbine rotor assembly. Second, the leakage of cooling air from its intended flow path starves the relatively thin-walled nozzle vanes and other internally air cooled portions of the gas turbine engine of their required cooling air. Such starvation of cooling air permits rapid oxidation and thermal failure of those components exposed to extremely high temperatures. Third, since the cooling air is normally bled from a compressor portion of the gas turbine engine, the leakage of cooling air past the aforementioned seal represents a waste of work done on that cooling air by the compressor portion. Unfortunately, the existence of such an improperly installed seal is usually diagnosed, if at all, only after the gas turbine engine has been fully assembled and operated. Thus, repair of the incorrectly installed seal is usually both time consuming and very costly.
Various methods have been devised to install a radially-resilient seal between two telescopically assembled elements. For example, prior to the installation of a piston and piston ring subassembly into a combustion cylinder of a reciprocating internal combustion engine, it has been conventional to temporarily place an annular piston ring compressor in stationary coaxially abutting relationship against an open end of the combustion cylinder. One known annular piston ring compressor is a one-piece sleeve having a tapered inside wall through which the piston and piston ring subassembly is slidably inserted into the combustion cylinder.
However, once the piston and piston ring subassembly is installed in the combustion cylinder, this piston ring compressor performs no other function and must be removed from the engine to permit further assembly of the engine. Furthermore, this piston ring compressor is not usable for other types of telescopic assemblies, for instance those found in the above described gas turbine engines, where the telescopic assembly of a piston ring carrier and an overlapping housing occurs within a substantially imperforate outer casing. Such a configuration having an outer casing already in place not only obstructs the assembler's view of the telescopic assembly but also completely obstructs the assembler's access to that internal region for insertion and removal of a typical piston ring compressor.
Another typical problem with gas turbine engines is successfully minimizing the amount of heat transferred during operation from the relatively hot stator nozzle assembly to the outer casing of the gas turbine engine. Minimizing such heat transfer harnesses more usable energy for driving the turbine rotor assembly and also keeps the outside surface temperature of the outer casing from becoming unacceptably high. As shown in U.S. Pat. No. 4,166,878 issued to Thompson et al on Sept. 4, 1979 and U.S. Pat. No. 3,864,056 issued to Gabriel et al on Feb. 4, 1975, it has been conventional to provide an annular heat shield which is disposed within the outer casing to prevent transfer of heat that is radiated outwardly from components directly exposed to the hot combustion gas stream.
The present invention is directed to overcoming one or more of the problems as set forth above.